I have been trying to stick to only buying fabric for particular projects that have been planned.
But, that said, I do have to admit that "my stash" that is a lot of random purchases does come in handy when I'm looking for a particular color or such.
We are 15 miles away from the nearest LQS (with a minimal offering) so that I justify some of my online purchases.
But, a good sale or discount always gets me in the mood to purchase fabric whether I need it ornot.